Questions?

Skills

Mega Pro Mini - 3.3V

Description: Do you need “Mega” power in a “Mini” package? We can do that! We’re continuing our Pro series of Arduino-compatible microcontrollers with the addition of the Mega Pro Mini. This is a 3.3V microcontroller running a version of the stk500v2 bootloader at 8MHz. In order to shrink the Mega Pro down to its minimum footprint, we’ve condensed the board layout, removed the barrel jack footprint and replaced the traditional Arduino-style headers with compact vertical JST connectors.

The Pro series is meant for users that understand the limitations of system voltage (3.3V), lack of connectors, and USB off board. This board connects directly to the FTDI Basic Breakout board and supports auto-reset.

Note: If you are using Arduino, modifications were made to the bootloader to support the 3.3V system, you will need to download and install a new board definition so that the Mega Pro can be programmed in the Arduino environment. The .zip archive below contains all of the files that you’ll need including a “readme” file with simple instructions for how to install them. OR you can use Wiring and not worry about this since the board is officially supported.

Not sure which Arduino or Arduino-compatible board is right for you? Check out our Arduino Buying Guide!

IS there a mating connector for the port pins that could be used on a shield? By this I mean a surface-mount connector that would go on a shield board and plug into his board. I did some research on JST’s web site but cannot seem to find one.

Can someone explain to me why the board has an 8MHz external resonator but has the fuse settings in the Arduino 1.0 boards.txt set to internal oscillator? Surely this makes the external resonator obsolete?

Ordered two back on 6/21 and can only rarely get them to load with Arduino 0022 or Arduino 1.0. Sparkfun tech support has same issue, but no resolution yet, and say they may just give up and obsolete the board. I am a great Sparkfun customer, and I committed to a project that needs this board; super bummed!. Any ideas out there? Really appreciate any help.

I don’t know if you’ve found a solution yet, but I also had the same problem when using the Sparkfun FTDI breakout. The way I got mine to work was to hold down the reset button right after clicking the upload button in the Arduino IDE, then releasing the button right before the IDE said “uploading.” Don’t know if you’ve tried that yet, but just a suggestion.

Very sorry about the problems you’ve had. It sounds like you received a poorly-attached part, please feel free to contact customer service if you find such problems in the future. We use and abuse our parts with this style of connector on a daily basis and rarely have this problem. Ensure that your FTDI/cable is not stressing the connector at a right angle, and as you say two drops of epoxy on the nubs on the back side of the board is good insurance.

I respectfully disagree; if you consider the pads the pivot-point that the connector is rotating against (stressing and breaking the solder connections in the process), firmly attaching the plastic block holding the pins to the board will help resist this rotation. If you apply epoxy to the two indexing pins on the back of the board, it will wick into the gap between the pins and holes, hopefully providing a better connection.

But the earlier point stands; if you’re not abnormally stressing this connector and it’s breaking, contact our customer service department and we’ll help you out.

I tend to think it is a mechanical design problem rather than a manufacturing error, as it came off too easily both times. All that is holding the current connector on there is six small smt solder pads, and two black dots of plastic (about 1mm in diameter) on the bottom of it. Give it a yank, and it comes off, taking the traces with it.

There are lots of epozy-type SMT adhesives around, why don’t you investigate them? The mechanical reliability of this connector doesn’t match the usual Sparkfun quality.

If you actually read the datasheet (Figure 31-3. Maximum Frequency vs. VCC, ATmega640/ATmega1280/ATmega1281) , these atmegas are actually rated for something like 12Mhz at 3.3v. I think because all the baud calculations have been done for 8mhz, people are just lazy.

John Luciani did a bootloader for the atmega328 that supports 12mhz…. just sayin'

There are other considerations besides laziness; the clock math does work out very nicely for a number of timing applications besides serial, the slower you clock a microprocessor the less power it consumes (unused cycles beyond what your code requires are basically waste heat), you’re that much further within the performance margins, etc.

I can confirm this issue: I have attempted for the past weekend to upload a bootloader to a custom Arduino Mega board I built, also running at 8 MHz. The full error appears immediately at the end of the bootloader burn processes. It is the exact same as the above and reads:

From reading and experimenting, it seems that this is a problem with the lock bits.

I have been able to upload sketches with my AVRISP mkII with no problem, and have also been able to upload the standard Aruduino Mega 16 MHz bootloader without this error (though of course it won’t work – was just testing to make the verification error go away). I have attempted to modify the makefile for the existing stk500v2 bootloader to include compatibility at 8 MHz, but so far have been unsuccessful – the bootloader will upload successfully, but I will have timeout() errors when attempting to upload the sketch (so maybe something with the baud rate?).

For completeness, here is my attempt to change “Makefile” in the “stk500v2” directory of the Arduino source:

I haven’t yet tried to burn a new bootloader to my Arduino Mega Pro 3.3V (I have the non-mini board but am posting here to keep the topic together) because I’m not sure whether it would be better to try on one of those boards or worse to possibly incapacitate my one USB-programmable system.

Clearly, someone at Sparkfun got this working for their boards, so I’m going to email their tech support and re-post with what we find out.

And in case it is useful, I am running Ubuntu 14.04, 64-bit, and am using Arduino 1.0.5.

Customer Reviews

4 out of 5

SparkFun is an online retail store that sells the bits and pieces to
make your electronics projects possible. Whether it's a robot that can
cook your breakfast or a GPS cat tracking device, our products and
resources are designed to make the world of electronics more accessible.

In addition to products, SparkFun also offers
classes and online tutorials to help educate
individuals in the wonderful world of embedded electronics.